Hitherto, a gap is defined between each of steps and each of skirt guards of a passenger conveyor so as to prevent contact of each of the steps with the skirt guards at the time of traveling. Each of the steps is caused to travel along a traveling direction thereof by step chains which are arranged on both side surfaces of each of the steps. In some cases, each of the step chains is extended due to a temporal change or an external factor. When the step chains are not evenly extended, in some cases, each of the steps may travel while being inclined with respect to the traveling direction. In such a case, the side surfaces of each of the steps may be brought into contact with the skirt guards and cause damage on the skirt guard.
In view of the circumstance described above, there has been disclosed an apparatus having the following configuration. Specifically, at a position at which step horizontally move and at which postures of the steps are not corrected, a distance sensor configured to measure a distance to a side surface of the step is disposed, and a change in width of a gap between the steps is measured based on measurement values given by the distance sensor, to thereby detect extension of chains for the steps (for example, see Patent Literature 1). Moreover, there has been disclosed an apparatus having the following configuration. Specifically, sensors are arranged on one end side and another end side of a landing plate, and it is determined that inclination of a step surface is abnormal when a time difference in passage of the step surface through the sensors exceeds a threshold value (for example, see Patent Literature 2).